Medical imaging instruments are often utilized by doctors and other medical professionals to conduct non-invasive examinations. That is, medical imaging instruments, including X-ray, magnetic resonance (MR), computed tomography (CT), ultrasound, and various combinations of these instruments/techniques are utilized to provide images of internal patient structure for diagnostic purposes as well as for interventional procedures. Such medical imaging instruments allow examination of internal tissue that is not readily examined during normal visual or tactile examination. Applications include imaging in the areas of mammography, urology and brachytherapy.
Medical imaging devices typically allow for generating 3-D images of internal structures of interest. Such 3-D imaging may improve the accuracy and/or reliability of medical diagnosis. For instance, a medical imaging device may be utilized to generate a 3-D model or map of a patient's prostate such that one or more biopsies may be taken from a desired location of the prostate. For purposes of prostrate imaging, image acquisition and guidance may be provided by a transrectal ultrasound-imaging device (TRUS). In such an application, the ultrasound-imaging device may be inserted into the rectum of a patient to generate an image. Such images may be utilized to take one or more biopsies from a prostate location of interest and/or implant therapy seeds at one or more desired locations in a brachytherapy procedure.
In order to generate 3-D images, many medical imaging devices obtain a plurality of images (e.g., two dimensional images) and combine these images together to form a 3-D image. Traditionally, medical practitioners have manipulated a medical imaging instrument by hand for medical image acquisition and/or treatment. However, in instances where it is desirable to obtain multiple 2-D images for 3-D image generation, manual manipulation of the device may result in the type of unconstrained movement between images that makes registration difficult or impossible. That is, unconstrained (e.g., random) movement of a medical imaging device between the acquisition of individual images makes it more difficult to properly align (e.g., spatially register) the different images for purposes of generating an accurate 3-D image. Accordingly, a number of holding and manipulating/positioning assemblies have been proposed wherein a holder interfaces with an imaging device such as an ultrasound probe. Such a holder is then interconnected to one or more mechanical armatures and/or actuators such that the probe may be controllably positioned, advanced and/or rotated. In such systems, the position of the probe is known and movement of the probe (e.g., rotational, linear, etc.) is typically limited to a single degree of freedom. In this regard, the offset (e.g., angular or linear) between images is known. Accordingly, registration of such images is simplified.